This study compares computer registry data on coronary bypass surgery from several centres in Canada and the United States to assess current trends in patient profile, and looks at demand and resources available for this form of treatment. A computerized registry established at the Royal Victoria Hospital in 1982 was used to document the profile of patients undergoing coronary artery bypass graft. Comparing 1988 to the previous six years (1982-87), a significant increase was found in patients with unstable angina (P less than 0.001) and abnormal left ventricular function (P less than 0.015) among those operated. The incidence of emergency operations also increased (P less than 0.001). The patient profile was similar to that of the Toronto university hospital population and many major United States university hospitals. The incidence of coronary artery bypass graft per 100,000 population, however, is much greater in the United States than in Canada (120 versus 56). Resources in many Canadian centres appear to be insufficient to meet demand for this type of surgical intervention.